Re: account enumeration

[Zate <zate75 () gmail com>]

That sounds like a viable solution in principle.  I'd couple that with
making sure you use persona to authenticate, not email address.  So start
registration with an email address, it checks to see if that email is
associated with an account.  It either emails a link to continue or to
recover.  Zero indication to the attacker is returned on the validity of
the email address.

Same with account recovery, enter an email address, we email you a recovery
link with zero feedback on whether an account exists.

Now when it comes time to add a persona, you are still going to have to
check that persona to make sure it's unique.  I've seen some games (and
most of my experience in this was working at a game company) start to use
persona with a random 4 digits on the end.  So if  I want Bugsbunny, on the
back end it does a check, grabs me a random 4 digits not associated with
Bugsbunny and I end up with Bugsbunny.7834.  I get the persona I want, and
there is not "is it used" check.

Inside the app/game you can drop the 4 digits from display, just use them
as a uniqueness identifier.

This solves, I think, a number of issues.  Thoughts on that?

btw, it's still a good idea to use some anti-automation stuff in various
places such as account reset, registration etc etc.  I'm also a big fan of
OTP when machine/browser changes (ie logging in from a previously unknown
IP)



Zate



On Thu, Dec 20, 2012 at 10:05 AM, Robin Wood <robin () digininja org> wrote:

> Hi
> I'm writing a report and have identified the web app is vulnerable to
> account enumeration because of the difference in messages on the
> forgotten password page. This can be fixed by giving a generic message
> regardless of whether the account exists in the system or not.
>
> That got me thinking about the registration system. The site requires
> a unique user name which means the registration page is vulnerable to
> the same issue (see Sythe from Chris John Riley
> http://blog.c22.cc/2012/10/03/scythe-framework/ ) but here it is worse
> as you can't give a generic message, you have to say "sorry, the user
> name is taken" if it is.
>
> So I was wondering if there is a way to do a secure registration
> system which does not leak information about existing accounts. The
> only option I could think of was to use email address as the user name
> and when someone wants to register they start the process by just
> entering their address. If the account exists they are sent info to
> tell them that someone has tried to register with that address and
> offers the ability to recover the account or to report the attempt. If
> they are not in the system it gives a unique registration link which
> allows them to continue to register.
>
> Does this sound like a workable solution?
>
> Does anyone else have any other options?
>
> Robin
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